Are there events in your past for which you feel a sense of regret?
Dictionary.com defines regret as 'a feeling of sorrow or remorse for a fault, act, loss, disappointment, etc.' I would define tweak this definition slightly, to be more about a sense of unhappiness with an event, action or experience in the past. The emotion is attached to our own role in it.
Regrets are often identifiable by the language you use to describe them. Words such as 'I wish I had...', 'I should have...' are indicators of regret.
It is useful to take a look at our emotions around something when those phrases crop up and come to peace with however we behaved or whatever we did in that circumstance. If one doesn't come to peace with past actions, the collection of regrets can accumulate. No one would describe the feeling of regret as a positive emotion; it leaves you feeling sad and powerless.
What if you were kind to yourself? Put yourself in the shoes of that past you, and give yourself a break. Undoubtedly, you did the best you could with what you had or what you knew at the time. Or, you made an honest mistake, not realizing the impact of your actions. You have influence over your attitude towards that past event, and you can reframe it so you are at peace with the outcome.
Going through a process of forgiving yourself, and giving that past you a heartfelt hug, can free you up immensely. It can give you courage to continue to try again and again, without fear of failure. We all do things that in hindsight we wish we had done differently. It is part of being human. Being forgiving is a gift that you likely offer to others, so why not to yourself?